The present invention relates to a device and method for detecting insects in a structure and, more particularly, to a device and method for nondestructive testing of wood and wooden structures for the presence of wood destroying insects using microwave radiation.
Biological attacks caused by wood destroying fungus, borers, termites, carpenter ants and the like are a major problem for structures made wholly or partially of wood. Such attacks can cause considerable damage to wooden structures.
Known methods for the damage assessment of wooden structures and detection of wood damaging insects are mostly based on visual inspection and mechanical collectors (e.g., traps) of wood destroying insects. There are a few patents that discuss using the acoustic emissions from the insects to detect the insects, but there is no evidence of successful implementation of this technique in practice. In fact, only visual inspection is currently performed to detect damage. In most cases, the visual inspection detects only damage, not the presence of the insects. Such inspection is limited only to assessable parts of the structure. As a result, most of the structure is not inspected. Moreover, even if the damage was visually detected and the structure was treated, there is no means to ensure the effectiveness of the treatment, since there is no means of determining the presence of the still living insects in the structure. Similarly, there is no known effective method for evaluating damage caused by wood destroying insects other than the visual inspection thereof.
In addition, there is no known insect detection device that is able to distinguish motion signals indicative of the presence of insects in a structure and signals caused by movement of the device itself. Since electronic insect detection devices typically contain sensitive components designed to detect the movement of insects, any movement of these devices can lead to the false indication of the presence of insects in a structure. For instance, hand tremors of an operator holding an insect detection device cause significant movement thereof. In addition, if an insect detection device is placed against a structure to be tested, structural vibrations caused by wind, appliances or nearby moving vehicles can lead to the movement of the insect detection device. Also, moving vehicles and people that pass behind a structure undergoing testing can cause motion signals that can lead to false indications of the presence of insects in a structure. As a result, it would be difficult for an operator of an insect detection device to distinguish false indications of the presence of insects in a structure from the actual presence of insects therein. Consequently, this could lead to increased time and costs for testing a structure and/or inaccurate test results.
U.S. Pat. No. 3,754,254 to Jinman (the xe2x80x9cJinman ""254 Patent) discloses a device for detecting moving targets by the doppler shift of radiation reflected or scattered by a target that is illuminated by transmitted radiation. The Jinman ""254 Patent focused on the problem of an interfering signal having a frequency difference from the transmitted radiation lying in the range of the expected doppler shift, which would give a false target indication. The Jinman ""254 Patent discloses that modulating the frequency of the transmitted radiation can mitigate such problem, so that the scattered or reflected radiation has a coherence with the transmitted radiation. The Jinman ""254 Patent further discloses that a device performing the aforesaid function is particularly applicable to intruder alarm systems.
U.S. Pat. No. 6,313,643 to Tirkel (the xe2x80x9cTirkel ""643 Patentxe2x80x9d) has been distinguished from the invention disclosed by the Jinman ""254 Patent on the basis that the termite detection system disclosed therein includes a transmitter adapted to transmit a xe2x80x9cnear fieldxe2x80x9d microwave signal into a structure and a receiver adapted to receive reflected signals that are indicative of the presence of insects in the xe2x80x9cnear fieldxe2x80x9d of the microwave signal. However, the Tirkel ""643 Patent does not disclose that the termite detection system is able to detect the presence of termites within the xe2x80x9cfar fieldxe2x80x9d of the signal generated thereby. As a result, the termite detection system""s function is substantially constrained. In addition, the Tirkel ""643 Patent does not disclose whether the termite detection system is able to distinguish output signals indicative of the presence of termites in a structure and output signals caused by movement of the termite detection system itself. As a result, it would be difficult for an operator of the termite detection system disclosed by the Tirkel ""643 Patent to distinguish false indications of the presence of insects in a structure from the actual presence of insects therein and, therefore, could lead to increased time and costs for testing a structure and/or inaccurate test results.
Accordingly, what would be desirable, but has not yet been developed, is a reliable device and method for detecting the presence of wood destroying insects in wood and wooden structures.
In accordance with the present invention, an insect detection device and method employ a plurality of transceivers, each of which generates separate and distinct microwave signals and receives separate and distinct signals reflected from a structure being tested for insects. The reflected signals received by each of the transceivers are processed, for instance by a microprocessor, so as to provide output signals that indicate the presence or absence of insects in the structure being tested.
By providing a plurality of transceivers, the present invention allows a user to distinguish between false indications of the presence of insects in a structure and the actual presence of insects therein. Since most insects, such as termites, ants, etc., move along narrow paths, only one or a couple of the transceivers will detect the insects"" motion, while the remaining transceivers will not detect such motion. If a condition that would trigger a false indication of the presence of insects in a structure occurs, such as hand tremors, structural vibrations, objects passing behind the structure being tested, etc. (i.e., non-insect motion), all, or substantially all, of the transceivers will receive a positive signal indicative of the presence of insects in the structure. In this case, the microprocessor""s algorithm enables the detection of insects in the structure being tested despite the existence of motion signals caused by such non-insect motion, whereby false and actual indications of the presence of insects in the structure being tested can be distinguished from each other.
In accordance with other aspects of the present invention, each of the transceivers is provided with an antenna adapted to transmit microwave signals generated by its corresponding transceiver and to receive the reflected signals to be received by its corresponding transceiver. In use, each of the transceivers and its corresponding antenna are positioned a preselected distance from the portion of the structure being tested. The distance is specifically selected such that the portion of the structure being tested lies within each of the antennas"" far field.
In addition, the device is provided with partitions that shield the antennas from each other, thereby reducing any interference between the microwave signals transmitted by the antennas and between the reflected signals received thereby. The partitions also shield the antennas from signals that are reflected by portions of the structure that are not, at that particular time, subject to testing, as well as from signals generated by extraneous sources such as television stations and radars. Finally, the device is provided with a demultiplexer that sequentially activates and sequentially deactivates the transceivers such that the transceivers are activated and deactivated in succession. In this regard, only one of the transceivers generates microwave signals and receives reflected signals from the structure at a particular time.
Specifically, the present invention has been adapted for use in detecting wood boring insects, such as termites, ants, etc., in wood and wooden structures. However, the present invention can be utilized to detect other insects and/or used to test structures made from materials other than wood.
Further features and advantages of the invention will appear more clearly on a reading of the detailed description of the exemplary embodiments of the invention, which are given below by way of example only with reference to the accompanying drawings.